The invention relates to a process for the magnetooptical measurement of magnetic fields. It also relates to a system performing this process and to a measuring cell adapted to said system.
It is known to accurately measure the value of a magnetic field at a given point. This accuracy requirement leads to the design of equipment having a sensitivity such that their measurements can be affected by fluctuations of the ambient magnetic field. Thus, for example, certain magnetometers make it possible to measure weak magnetic fields of approximately 1 nano-Tesla, while convetionally the ambient magnetic field has variation amplitudes ranging between a few dozen to a few hundred nano-Tesla in a frequency spectrum extending from continuous field to a alternating field having a frequency of few dozen Hertz.
For carrying out precise magnetic field measurements and in order to be able to correct them as a function of the ambient magnetic field, it is possible to use several magnetometers. Precautions must then be taken to ensure that the magnetometers do not impact the measurements of one act one another.
French Patent application No. 2,471,608, published on 13.8.1982, its first addition 2,517,831 published on 10.6.1983 and French Patent application No. 8,311,073 filed on 4.7.1983 describe magnetometers, whose common basic cell is constituted by a polarized light source, a thin film having a significant magnetooptical effect, an analyzer and an electric current-light conversion and detection system. To these elements are added a feedback and modulation solenoid, as well as a pair of saturation magnets or coils producing a polarizing magnetic field.
When several magnetometers are used in a reduced volume, which is the case for triaxial measurements, or when the basic cells are used for measuring magnetic field gradient vectors, the sensitivity of the measurement is effected by the existence of continuous polarizing magnetic fields, which mutually deform the magnetic field lines. Attempts have been made to reduce or eliminate these continuous polarizing magnetic fields.
The invention provides a solution making it possible to eliminate the polarizing magnetic field of the magnetometer. It also has the advantage of operating with a magnetometer probe of simplified design and reduced overall dimensions.